Overview
When installing a circulator pump to a potable plumbing system, the method of connection between the circulator pump and the pipes becomes desirable information. There are a few different methods of connecting circulator pumps to water circulation systems but know that the circulator pump will still operate in any plumbing system regardless of the connection type.
Flanges

Flange type pump
Flanges are pieces of metal that are the medium of connection between the circulating pump and the plumbing piping. Most circulator pumps use a universal flange size although the orientation of the flange may be different. Some pumps have flanges that run parallel to the pump while others will have flanges that run perpendicular to the circulator pump. Flanges have two holes that are used as a connection to the circulator pump. The larger hole in the middle is for the pipe and is sized to match the exact piping size. The flanges are threaded female connections for hard piping.
Sweat

Sweat type pump
Sweat connections are common for hot water recirculation applications because of its ability to be quickly added to the system. Working with a sweat-type connection circulator pump is much like working with normal copper piping and any of its elbows or fittings. The sweating process is still done the same way and you will still need a furnace to achieve a secure connection. You will notice that your circulator pump is a sweat type if, instead of a flange base, there is a single hole with no threading that is sized for your specific plumbing piping.
Threaded

Threaded type pump
Threaded connections might very well be the easiest connections to make because they don’t require anything in addition to the circulator pump. Flanges require bolts and sweat connections require a furnace as well as a material to make the connection. Like the name suggests, threaded circulator pumps can also be called female NPT (national pipe thread) which means that it is receiving the threading of the male piping.

